Barcelona overcame a sluggish start to progress to the Copa del Rey semi-finals with a 3-1 win (5-2 on agg) over Athletic Bilbao at the Nou Camp on Wednesday.

Barca held a 2-1 lead after a narrow first-leg victory seven days ago, but Inaki Williams deservedly put Athletic ahead on 12 minutes after springing the offside trap and slotting home.

Luis Enrique's side struggled to find their fluency in a disjointed first-half, but drew level after the break through Luis Suarez, and Gerard Pique headed Barca in front with ten minutes to play before Neymar put the icing on the cake with a stunning strike in stoppage time.

The Lions started the brighter as the two sides faced off for the sixth time this season, but it was Barca who carved out the first opportunity.

Thomas Vermaelen rose highest to head home Lionel Messi's corner on nine minutes, but the goal was ruled out for a shirt-pull on Mikel Rico, and Bilbao took full advantage three minutes later. Williams latched on to Aritz Aduriz's perfectly-judged pass and rounded Marc-Andre Ter Stegen before tapping into the empty net.

The away side were good value for their lead and should have extended it before the break. Javier Eraso first went close, guiding his volley wide from six yards before Markel Susaeta fired his attempt over after Mikel Balenziaga's deep cross was headed back across goal.

The flurry of chances for Athletic prompted whistles from the Nou Camp crowd unused to such dominance from a visiting team, and it did illicit a reaction from Enrique's side.

Neymar was denied a penalty twice in quick succession ten minutes before the break, and Iago Herrerin did well to smother the Brazilian after a quick one-two with Suarez had put him in.

Messi, quiet throughout, had two opportunities just before the interval, firing a free-kick over before his low shot deflected wide.

Barca improved in the second half, and were level within eight minutes as Suarez swept home Messi's low centre. Sergi Roberto chipped through for the Argentine, and when his cross was missed by Ivan Rakitic, Suarez was on hand to slide past Herrerin.

Neymar, often the main target of firm challenges from Bilbao defenders, was next to test Herrerin as the Athletic 'keeper came under heavy pressure in the closing stages.

He made four smart stops in a two-minute spell, including one from the Brazilian, before his resistance was broken by Pique, who headed home from close range after Dani Alves' measured cross.

Athletic, who then needed two goals to progress, pushed forward in the final five minutes but left plenty of space behind as Messi nearly presented Suarez with a tap-in shortly after going close himself.

But it was left to Neymar to put the exclamation mark on the display with a fearsome strike into the top corner with seconds remaining.

In the evening's other quarter-final, Atletico Madrid crashed out to Celta Vigo with a 3-2 defeat at the Vicente Calderon. After a goalless first-leg, Pablo Hernadez put the visitors in front before Antoine Griezmann equalised.

Celta took a commanding lead shortly after the break through John Guidetti's long-range strike and Hernandez's second, and they held on after Angel Correa's late finish set up a nervy finale.

Mirandes face Sevilla tomorrow while Valencia play Las Palmas in the remaining quarter-finals, with the semi-final dates set for February 3 and February 10.